a. Field of the Invention
This invention relates to a method and an arrangement for lining chambers and galleries, especially mining and tunnelling galleries, with resilient steel supporting frames consisting of a number of box-like segments capable of being slid into one another and which thus, at least in the zone of overlap, constitute a closed tube.
B. Description of the Prior Art
The resistance of the gallery lining to changes of shape, which are caused by displacements or other changes in position of the adjacent rock, depends with the resilient lining on the load bearing capacity of the lining sections and on the so-called insertion resistance of the resilient structural members. Lining elements are known which are used as a resilient lining in underground mining and tunnelling, and which consist of a number of section segments placed in one another in a like manner and which overlap in a certain region. In the region of overlap the section segments are pressed against one another by clamp connections. These connections have the task of bracing the section segments with a prescribed force, which is produced by screwing, so that when the lining frame is placed under load as the result of rock pressure, the frictional resistance of the mutually braced sections is only overcome at a value dependent on the bracing force. The lining arch then at any time thrusts inwards jerkily only by small amounts, whilst the section segments slide into one another. Such a lining is known, for instance, from German Patent Specification No. 1,201,285.
The insertion resistance obtainable with the known resilient lining amounts, according to measurements made also below ground, to 5 - 10 tonnes. These relatively unfavourable values come about because the connections used hitherto and working on the basis of frictional forces transmit the forces from the rock more or less unequally, because the friction values vary, the screws, clips and other fastening elements stretch under the loads applied, the structural elements have dimensional inaccuracies, or the clips become slack and change their position. Moreover, the serviceability is affected by the carefulness of the service personnel, as the section segments are braced mutually and placed in one another in a like manner in the region of overlap, and adequate overlaps and satisfactory stressing force must be allowed for without fail when tightening the tie nuts. The measurements already cited show, however, that as a rule the frictional forces generated by the bracing lead to only a small insertion resistance.
Again and again it has been sought to raise the insertion resistance by improvements and modifications to the connecting elements. Further, in regard to mining there is the requirement to make the load bearing capacity, determined by the insertion resistance, adjustable or at least capable of being affected by suitable devices. Such endeavours are, however, rendered difficult in that the lining used in mining and tunnelling must be simple, robust and practical.
A steel section is now known of approximately U-shaped cross-section having a section bottom with webs and flanges slightly inclined to one another toward the open section side. At its longitudinal sides, the section bottom of this section passes into a graduation directed to the open section side, to which webs are attached. The flanges strengthening the webs point to one another. When assembling the steel section into a lining frame, the steel section segments overlapping at the connecting ties, respectively strengthening points, are pushed one into the other in an unlike manner. During the insertion, the inner surfaces of the flanges of the outer steel section segment correspond with the outer flanges of the graduations of the inner steel section segment, whilst the flanges of the inner steel section segment bear against the inner surfaces of the section bottom of the outer steel section segment, and in the region of the webs there results an off-thrust against one another as well as against the inner surfaces of the graduation of the section bottom. In this way an insertion resistance, which is, however, not capable of being determined precisely beforehand, is generated on insertion. A steel section of this type suitable for lining frames is disclosed in German Patent Application No. P 25 50 577.5.
In order that the sections can be fitted into each other, the end of one steel section segment is sufficiently widened for the end of the steel section segment to be inserted, which is compressed for better fitting, to be pushed in easily. When inserting the compressed inner segment into the widened outer segment, a resistance to a change of shape in the rolled section, which makes the insertion much more difficult and thus sets up a marked insertion resistance, must be overcome.
Trials with lining frames of this kind have shown, however, that the insertion resistance is not adequate. It is only slightly above or equal to that of the known lining with sections lying inside one another in a like manner.